1. Field of the Invention
This invention relates generally to knitted fabric, and in particular to a warp knitted fabric incorporating laid-in strips of material. The fabric is applicable for use as a canopy in a covering structure in order to provide shade and other protective covering. It will be convenient to hereinafter disclose the invention in relation to that exemplary application, although it is to be appreciated that the invention is not limited thereto.
2. Description of the Prior Art
In a typical application, a knitted canopy fabric such as shade cloth is supported by a structure which extends over an agricultural or horticultural crop or orchard to be protected, or an area to be shaded or otherwise protected. The structures take a variety of forms, but have in common that it is desirable to stretch the fabric over the structure so that it remains taut in use.
One form of knitted fabric provides a plurality of longitudinally extending flexible strips laid into a knitted thread framework. The framework is formed by spaced apart longitudinal and transverse connection threads, Respective strips extend along the spaces defined between adjacent longitudinal connection threads, with the strips having a width that corresponds to the width of the spacing between those threads. The transverse connection threads extends across each side of the strips between the adjacent longitudinal connection threads so as to retain the strips in position. The strips are thermo-mechanically fixed to the framework to assist in that retention.
One such form of knitted fabric is disclosed in Australian patent 577033.
A warp knitted fabric tends to change dimension when stretched. Although thermosetting of the fabric following knitting dimensionally stabilises the fabric to a substantial extent, the significant forces applied to the fabric during installation to and support on a structure tends to cause further stretching. Where that stretching is in a lateral direction, i.e. transverse to the direction in which the fabric was knitted, then in the case of fabric incorporating laid in material strips gaps appear between the strip edges and longitudinal threads. As a result, the covering integrity of the fabric is compromised. In particular, the fabric looses its rated shade factor, and may also suffer a reduction in the ability to protect against, for example, hail.
An object of the present invention is to provide a knitted fabric incorporating laid in material strips which maintains its protective qualities when in use stretched over a support structure.
With that object in mind, the present invention provides a warped knitted fabric comprising:
an open framework of longitudinally and transversely extending knitted threads, the longitudinally extending threads being spaced apart a predetermined distance; and,
a plurality of material strips laid in the open framework along the spaces between the longitudinally extending threads, the material strips each having a width which is greater than the predetermined distance between adjacent longitudinally extending threads so as to extend fully between the adjacent threads and maintain that full extension upon lateral stretch of the fabric.
Preferably, the knitted threads form an array of thread connections extending in parallel spaced apart rows along the longitudinally extending threads. The material strips preferably have opposed longitudinal edges that abut respective rows of the thread connections.
Preferably, the rows of thread connections are provided by pillar stitches.
Preferably, the material strips have opposed longitudinal faces, and the transversely extending threads extend across the spaces between the longitudinally extending threads and over the opposed faces.
Preferably, the threads extending across the spaces are provided by thread underlaps.
The material strips may extend along each space between the longitudinally extending threads. Alternatively, the material strips may extend along only some of those spaces between the longitudinally extending threads. Thus, in this alternative some individual spaces or groups of adjacent spaces may carry material strips and be interposed with individual or groups of spaces not carrying material strips.
Preferably, the material strips have a curved transverse profile. That profile tends to flatten toward a planar transverse profile upon lateral stretch of the fabric.
Preferably, the material strips have less longitudinal stretch than the framework thereby reducing overall longitudinal stretch of the fabric.
The threads are preferably composed of heat shrinkable plastic filament, and the fabric is heat shrunk thereby to thermo-mechanically fix the fabric.